An operating system, or OS, is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer operating system, a computer would be useless. As computers have progressed and developed so have the types of operating systems. Below is a basic list of the different types of operating systems and a few examples of operating systems that fall into each of the categories. Many computer operating systems will fall into more than one of the below categories.

BATCH SYSTEM

TORQUE Resource Manager

(Terascale Open-Source Resource and QUEue)

An open-source distributed resource manager providing control over batch jobs and distributed compute nodes. It is a community effort based on the original PBS project and, with more than 1,200 patches, has incorporated significant advances in the areas of scalability, fault tolerance, and feature extensions contributed by NCSA, OSC, USC, the US DOE, Sandia, PNNL, UB, TeraGrid, and many other leading edge HPC organizations. TORQUE can integrate with the open source Maui Cluster Scheduler or the commercial Moab Workload Manager to improve overall utilization, scheduling and administration on a cluster.

TORQUE provides enhancements over standard OpenPBS in the following areas:

It benefits are initiate and manage serial and parallel batch jobs remotely (create, route, execute, modify and/or delete jobs); define and implement resource policies that determine how much of each resource can be used by a job; apply jobs to resources across multiple servers to accelerate job completion time; and collects information about the nodes within the cluster to determine which are in use and which are available.

INTERACTIVE SYSTEM

Windows XP Professional

An Automatic Teller Machine is a good example of a form-based program where users are given a tightly controlled set of possible actions. Data entry systems are frequently form-or dialog-oriented systems offering the user a limited set of choices but greatly relieving the memory demands of the earlier command line systems. Typical platforms previously used in ATM development include RMX or OS/2. Today the vast majority of ATMs worldwide use a Microsoft OS, primarily Windows XP Professional.

Windows XP Professional is designed for business and power-users. Also, a number of features unavailable in the Home Edition, including:

--} Ability to become part of a Windows Server domain; --} Sophisticated access control scheme; --} Remote desktop server, allowing the PC to be operated by another Windows CP user \over a Local Area Network (LAN) or Internet; --} Offline files and folders; encrypting file system; --} Centralized administration features, including Group Policies, Automatic Software Installation and Maintenance, Roaming User Profiles, and Remote Installation Service (RIS); --} Internet Information Services (IIS), Microsoft's HTTP and FTP Server; support for two physical central processing units (CPU), (Because thenumber of CPU coresandHyper-threadingcapabilities on modern CPUs are considered to be part of a single physical processor, multicore CPUs are supported using XP Home Edition.); --} Windows Management Instrumentation Console (WMIC): WMIC is a command-line tool designed to ease WMI information retrieval about a system by using simple keywords (aliases).

REAL-TIME SYSTEM

pSOS (plug-in Silicon Operating System)

A real-time operating system created in about 1982 by Alfred Chao. It had been develop and market for the first part of its life by his company Software Components Group. pSOS is a popular real-time operating system that is being primarily used in embedded applications. It is available from the Wind River Systems, a large player in the real-time operating system arena. pSOS is being used in several commercial embedded products. An example of its application is in the base stations of the cellular systems. pSOS rapidly became the RTOS of choice for all embedded systems based on Motorola 68000 family architecture, because it was written in 68000 assembler and was highly optimized from the start. Also modularized with early support for OS-aware debugging, plug-in device drivers, TCP/IP stacks, language libraries and disk subsystems. Then came the source-level debugging, multi-processor support and further networking extensions.

pSOS consists of 32 priority levels. In minimal configuration, the footprint of the operating system is only 12Kbytes. For sharing critical resources among real-time tasks, it supports priority inheritance and priority ceiling protocols. It support segmented memory management. It allocates tasks to memory regions. A memory region is a physically contiguous block of memory. A memory region is created by the operating system in response to a call from an application. Most modern operating systems, the control jumps to the kernel when an interrupt occurs. pSOS takes a different approach. The device drivers are outside the kernel and can be loaded and removed at the run time. When an interrupt occurs, the processor jumps directly to the ISR (interrupt service routine) pointed to by the vector table. The intension is not only to gain speed, but also to give the application developer complete control over interrupt handling.

HYBRID SYSTEM

WINDOWS SERVER 2008

One of Microsoft Windows' server line of operating systems , successor to Windows Server 2003 that was release to manufacturing on February 4, 2008, and officially released on February 27, 2008. Then Windows Server 2008 R2, was released to manufacturing on July 22, 2009. Like Windows Vista andWindows 7, Windows Server 2008 is built on Windows NT 6.x.

Powered by Microsoft NT kernel (best known example of a hybrid kernel), Windows Server 2008 is built from the same code base as Windows Vista; therefore, it shares much of the same architecture and functionality. Since the code base is common, it automatically comes with most of the technical, security, management and administrative features new to Windows Vista such as the rewritten networking stack (native IPv6, native wireless, speed and security improvements); improved image-based installation, deployment and recovery; improved diagnostics, monitoring, event logging and reporting tools; new security features such as BitLocker and ASLR; improved Windows Firewall with secure default configuration; .NET Framework 3.0 technologies, specifically Windows Communication Foundation,Microsoft Message Queuing and Windows Workflow Foundation; and the core kernel, memory and file system improvements. Processors and memory devices are modeled as Plug and Play devices, to allow hot-plugging of these devices. This allows the system resources to be partitioned dynamically using Dynamic Hardware Partitioning; each partition has its own memory, processor and I/O host bridge devices independent of other partitions. Server 2008 includes a variation of features including:

Software used on vast majority of Cisco Systems routers and current Cisco network switches. (Note that earlier switches ran CatOS). IOS is a package of routing, switching, internetworking and telecommunications functions tightly integrated with a multitasking operating system. In all versions of Cisco IOS, packet routing and forwarding (switching) are distinct functions. Routing and other protocols run as Cisco IOS processes and contribute to the Routing Information Base (RIB). This is processed to generate the final IP forwarding table (FIB, Forwarding Information Base), which is used by the forwarding function of the router. On router platforms with software-only forwarding (e.g., Cisco 7200) most traffic handling, including access control list filtering and forwarding, is done at interrupt level using Cisco Express Forwarding (CEF) or dCEF (Distributed CEF). This means IOS does not have to do a process context switch to forward a packet. Routing functions such as OSPF or BGP run at the process level. In routers with hardware-based forwarding, such as the Cisco 12000 series, IOS computes the FIB in software and loads it into the forwarding hardware (such as an ASIC or network processor), which performs the actual packet forwarding function.

Cisco IOS has a characteristic of command line interface (CLI), whose style has been widely copied by other networking products. IOS CLI provides a fixed set of multiple-word commands — the set available is determined by the "mode" and the privilege level of the current user. "Global configuration mode" provides commands to change the system's configuration, and "interface configuration mode" provides commands to change the configuration of a specific interface. All commands are assigned a privilege level, from 0 to 15, and can only be accessed by users with the necessary privilege. Through the CLI, the commands available to each privilege level can be defined. Most Cisco products that run IOS also have one or more "feature sets" or "packages", typically eight packages for Cisco routers and five packages for Cisco network switches. Each individual package corresponds to one service category: IP data; converged voice and data; security and VPN (Virtual Private Network). Beginning with the 1900, 2900 and 3900 series of ISR Routers, Cisco have revised the licensing model of IOS. Routers come with IP Base installed, and additional feature pack licenses can be installed as bolt-on additions to expand the feature set of the device. The available feature packs are: